During semiconductor manufacturing, a semiconductor wafer undergoes a plurality of process steps, each of which are performed by a specialized process tool. Pods are used to convey semiconductor wafers from one tool to another. An exemplary type of pod is referred to as a front-opening unified pod (FOUP). Each pod is capable of transporting a number of wafers of a specific diameter. For example, for wafers of 300 mm, a conventional FOUP has a capacity of 25 wafers, and can therefore carry 25 or fewer 300 mm wafers at a time. For wafers of 450 mm, a FOUP capacity of 25 wafers may also be used, but this FOUP size could be larger to accommodate the larger wafer diameter/thickness and the correspondingly larger wafer stack height within the FOUP. The pods are designed to maintain a protected internal environment to keep the wafers free of contamination, e.g., by particulates in the air outside the pod. Pods are also known for conveying other types of substrates, such as liquid crystal panels, rigid magnetic media for hard disk drives, solar cells, etc.
FIG. 1 shows a conventional loadport 10 configured to interface with a standard 300 mm, 25-wafer pod 70. Loadport 10 is attached to a front end of a process tool as described, for example, with reference to FIGS. 1 and 2 of U.S. Pat. No. 6,502,869, which issued Jan. 7, 2003 to Rosenquist et al., and is incorporated herein by reference in its entirety. For purposes of description, the “front” of loadport 10 is the side of loadport 10 facing the positive Y direction as indicated by coordinate axes 21. The “front” of pod 70 is the side facing the front of loadport 10.
Loadport 10 includes a tool interface 20. In the semiconductor industry, tool interface 20 is often in conformance with an industry standard referred to as “Box Opener/Loader-to-Tool Standard Interface” (BOLTS), commonly referred to as a BOLTS interface or a BOLTS plate. Tool interface 20 includes an aperture 22, i.e., opening. Aperture 22 is substantially occluded by a port door 30. Port door 30 forms a proximity seal with a boundary of aperture 22 to prevent contaminates from migrating to the interior 40 of the process tool. A proximity seal provides a small amount of clearance, e.g., about 1 mm, between the parts forming the proximity seal. The small clearance of the proximity seal allows air at a higher pressure to escape from the interior 40 of the process tool and sweep away any particulates from the sealing surfaces of the proximity seal.
Loadport 10 also includes an advance plate assembly 50 having an advance plate 52. In one embodiment, registration pins (not shown) mate with corresponding slots or recesses in the bottom support 72 of pod 70, to facilitate alignment of the pod 70 on the advance plate 52. Pod 70 may conform to industry standards for Front Opening Unified Pods (FOUPs) or a different standard. Advance plate assembly 50 has an actuator (not shown) that slides advance plate 52 in the Y direction between the retracted position shown in FIG. 1 and an advanced position that brings pod 70 into close proximity with tool interface 20.
A front surface 34 of port door 30 includes a pair of latch keys 60. Latch keys 60 include a post that extends away from port door 30 and is substantially perpendicular to port door 30, and a crossbar at the distal end of the post. The crossbar extends perpendicularly to the post to form a “T” therewith. Port door 30 includes an actuator that interacts with latch keys 60, causing latch keys 60 to rotate on the axis of the post. When the pod 70 moves to the advanced position and the port door 30 moves into the aperture 22, latch keys 60 are inserted into corresponding latch key receptacles 61 of pod door 74. Latch keys 60 are then rotated on the axis of the post, thereby interacting with a mechanism internal to pod door 74, causing pod door 74 latches to disengage from flange 75 of pod 70. An example of a door latch assembly within a pod door adapted to receive and operate with latch keys is disclosed in U.S. Pat. No. 4,995,430, entitled “Sealable Transportable Container Having Improved Latch Mechanism,” which is incorporated herein by reference. Another example is presented in U.S. Pat. No. 6,502,869, issued on Jan. 7, 2003 to Rosenquist et al., also incorporated herein by reference.
In addition to disengaging pod door 74 from the pod 70, rotation of the latch keys 60 locks the keys 60 in their respective latch key receptacles, thereby coupling the pod door 74 to the port door 30. A conventional loadport includes two latch keys 60, that are structurally and operationally identical to each other. Additionally, alignment pins 36 are provided to facilitate alignment between port door 30 and pod door 74, so that pod door 74 will be sufficiently aligned to enable passage through the aperture 22 toward the process tool interior 40.
In the conventional loadport 10, the port door 30 is connected to an arm 32. A position of the arm 32 is controlled by a movement mechanism that provides for movement of the arm 32 and port door 30 connected thereto in a vertical direction, as indicated by arrows 35, and in a horizontal direction toward/away from the tool interface 20, as indicated by arrows 33. By way of the arm 32 movement, the port door 30 can be moved through the aperture 22 to engage with/disengage from the pod door 74. Also, when the port door 30 is engaged with the pod door 74, the arm 32 can be moved to bring the port door 30/pod door 74 combination horizontally into the process tool interior 40, and vertically downward to clear the aperture 22 for access to workpieces 25 within the pod 70. In a complementary manner, the arm 32 can be moved to move the port door 30/pod door 74 combination through the aperture 22 so as to replace the pod door 74 within the flange 75 of the pod 70.